Lagerstroemia indica spot defoliation

Brown spots appear on the leaves of Alternaria punctata at the initial stage of infection, and then gradually expand to reddish brown with purple-brown edges, and dark spots or concentric wheel lines often appear in the center of the affected area. When the weather is wet, dark green to black mold can grow on the front and back of the affected area. In summer and autumn, the temperature is high, the humidity is high, the onset cycle is shortened, and the diseased spots on the leaves of autumn shoots increase rapidly. There are often 10 ~ 20 diseased spots on a diseased leaf, and many diseased spots merge into irregular large spots, that is, the leaves are perforated or broken, the growth is stagnant, and the withered coke falls off. Brown to grayish brown spots appear on petioles, 1 annual branches and long branches, and the edges are cracked. Young fruits appear 1~2 mm small round spots with blush, which turn brown or scab in the later stage. It affects the normal growth of leaves, often makes the leaves twisted and shriveled, and the diseased parts are scorched, easily blown off by the wind and incomplete. When the fruit is infected, the surface of young fruit will produce small black spots or rust spots. Sometimes the diseased part is taupe scab-like plaque, and there are cracks at the junction of the diseased part and the diseased part is not peeled off, which is limited to the epidermis of the diseased fruit, but sometimes the superficial pulp under the skin can be corked in a dry and rotting way.

The typical feature of brown spot disease is that there are brown smooth hemispherical spots on the front of fresh diseased spots, which can be used to diagnose brown spot disease in practical production.

Anthracnose mainly harms fruits. At the beginning of the disease, light brown spots appeared on the surface of the fruit. After swelling, the diseased part was round and sunken, and the fruit was soft and rotten, and developed into a cone toward the core. Many small black spots are formed on the surface of the lesion, which are arranged in concentric circles, and pink mucus overflows from the small black spots when wet. A few diseased fruits are dehydrated and shriveled into black hard fruits, which remain on the trees for a long time.